Polymer isolation

Methods for isolation of the product polycarbonate remain trade secrets. Feasible methods for polymer isolation include antisolvent precipitation, removal of solvent in boiling water, spray drying, and melt devolatization using a wiped film evaporator. Regardless of the technique, the polymer must be isolated dry, to avoid hydrolysis, and essentially be devoid of methylene chloride. Most polycarbonate is extmded, at which point stabiUzers and colors may be added, and sold as pellets. 

Alternative processes for polymer isolation have involved direct dmm drying of latex (84), extmsion isolation of coagulated cmmb (85), and precipitation/drying or spray-drying of the mbber as a powder (86). The powder can be processed directly in continuous compounding equipment (87). The manufacture and use of powdered CR has been reviewed (88). 

Unless mentioned otherwise, the properties listed are for the polymer isolated from the growth medium. 

There have been a number of different synthetic approaches to substituted PTV derivatives proposed in the last decade. Almost all focus on the aromatic ring as the site for substitution. Some effort has been made to apply the traditional base-catalyzed dehydrohalogenation route to PTV and its substituted analogs. The methodology, however, is not as successful for PTV as it is for PPV and its derivatives because of the great tendency for the poly(u-chloro thiophene) precursor spontaneously to eliminate at room temperature. Swager and co-workers attempted this route to synthesize a PTV derivative substituted with a crown ether with potential applications as a sensory material (Scheme 1-26) [123]. The synthesis employs a Fager condensation [124] in its initial step to yield diol 78. Treatment with a ditosylate yields a crown ether-functionalized thiophene diester 79. This may be elaborated to dichloride 81, but pure material could not be isolated and the dichloride monomer had to be polymerized in situ. The polymer isolated... 

Optimal conditions for ATRP depend strongly on the particular monomer(s) to be polymerized. This is mainly due to the strong dependence of the activation-deactivation equilibrium constant (A ), and hence the rate of initiation, on the type of propagating radical (Section 9.4.1.3). When using monomers of different types, polymer isolation and changes in the catalyst are frequently necessary before making the second block... 

Fig. 38. A Degradation experiments with pregel polymers isolated prior to the onset of macrogelation in 1,4-DVB polymerization [209] Variation of Mw ( ) and dz (O) with the time of ultrasonic degradation. The polymer sample was prepared at 5 g/100 mL monomer concentration and its initial Mw was 2.2 X106 g/mol. The dotted horizontal line shows Mw of zero conversion polymers ( individual microgels ). B Variation of Mw with the polymerization time t and monomer conversion x in 1,4-DVB polymerization at 5 g/100 mL monomer concentration. The region 1 in the box represents the limiting Mw reached by degradation experiments. [Reprinted with permission from Ref. 209,Copyright 1995, American Chemical Society].

Emulsion polymer isolation gives polymers in the shape of tiny hollow spheres called cenospheres. The pure polymers are rarely used. They are generally compounded with a variety of additives such as fillers, plasticisers, lubricants, pigments and stabilisers to provide a variety of materials with differing physical, chemical and electric properties. 

Ccdculated from sulfur anadysis of grafted polymer isolated after removal of starch by acid hydrolysis. 

In crystalline oxides and hydroxides of iron (III) octahedral coordination is much more common than tetrahedral 43). Only in y-FegOs is a substantial fraction of the iron (1/3) in tetrahedral sites. The polymer isolated from nitrate solution is the first example of a ferric oxyhydroxide in which apparently all of the irons are tetrahedrally coordinated. From the oxyhydroxide core of ferritin, Harrison et al. 44) have interpreted X-ray and electron diffraction results in terms of a crystalline model involving close packed oxygen layers with iron randomly distributed among the eight tetrahedral and four octahedral sites in the unit cell. In view of the close similarity in Mdssbauer parameters between ferritin and the synthetic poljmier it would appear unlikely that the local environment of the iron could be very different in the two materials, whatever the degree of crystallinity. Further study of this question is needed. 

A glass tube was charged with the step 2 product (0.45 mmol), 100 ml of toluene, and methyl methacrylate (0.50 mmol) and then stirred at ambient temperature for 3 hours while irradiating with UV light. Thereafter, the mixture was precipitated in a large quantity of -hexane, filtered, dried, and the polymer isolated in 65% yield having an Mn of 45,000 Da with a PDI of 2.11. 

The step 7 monomer (0.61 mmol) and bis(trimethylstenyl)bithiophene (0.61) were dissolved in anhydrous DMF with gentle heating and then treated with tetrakis(triphe-nylphosphine) palladium(O) (about 10 mol% based on the total amount of reagents) and the mixture reacted at 85°C for 6 hours. The solution was cooled to ambient temperature, filtered, and the polymer isolated. It was then successively washed twice with hydrochloric acid/chloroform, twice with ammonia solution /CHC13, and twice with water/CHCl3. The polymer was then precipitated in methanol, dried, and 0.38 g of product isolated as a red polymer having an Mn of 25,000 Da. 

To a stirred solution of the step 2 product (4.12 mmol) dissolved in 20 ml THF was added a solution of the lithium salt of (2,2-dimethyl-[l,3]-dioxolan-4-yl)-methanol in 10 ml THF and the mixture refluxed for 18 hours. Upon cooling to ambient temperature, THF was partically removed and a concentrated solution/suspension of the crude product added dropwise to water. The aqueous mixture was then acidified to pH 5-6 and the precipitated polymer isolated. The polymer was redissolved in 50 ml 2 1 and then dried in vacuo at 50°C for several hours. The organic solution was extracted twice with 30 ml saturated sodium chloride solution and once with 30 ml of water. The material was dried using MgSO filtered, concentrated, and redissolved in a minimum amount of acetone and then precipitated into 100 ml hexane. Hexane was decanted, dried in vacuo, and the product isolated as a pale yellow viscous liquid in 60-90% yield. 

A glass reactor was charged with W-(2,6-diisopropylphenyl)-2-(2,6-diisopropyl-phenylimino)propanamide-benzyltrimethylphosphine nickel (20 pmol) in toluene, bis(l,5-cyclooctadiene)-nickel (50p,mol) in toluene, and 5-norbomen-2-ol (4.49 mmol) were dissolved in toluene, and additional toluene (18.45 g) added so that the total volume of the toluene solution was 30 ml. The glass reactor was then sealed and ethylene continuously fed into the reactor at 100 psi and the mixture stirred for 20 minutes at 20°C. Acetone was then added to quench the polymerization and die precipitated polymer isolated by filtration, dried, and 0.518 g of product isolated. The activity of the catalyst was 105 kg mol lh 1. 

At ambient temperature a reactor was charged with triisobutylaluminium (6 mmol 1 M solution in hexane), 1-butene (334 g), propylene (817 g), and 1-hexene (119) and then heated to 70°C. The solution was then treated with 1 ml of the step 1 product and stirred for 1 hour. The mixture was cooled to ambient temperature and the polymer isolated having C3, C4, and monomer incorporations of 75.8, 19.5, and 4.7%, respectively, with a Tm and Tg of 94.2 and — 20°C, respectively. 

A reactor containing 10 ml of toluene and 10 ml of aqueous Na2C03 was treated with the step 2 product (1.0 mmol), 2,7-dipinacol boron-9,9-di-octyl-fluoiene (1.0 mmol), tetrakis triphenylphosphine palladium (0.01 mmol), and 0.16 ml of tricaprylmethyl-ammonium chloride. The mixture was then treated with a few drops of bromobenzene and then refluxed for 1 hour and treated with a few drop of phenyl boronic acid and then further refluxed 15 hours and cooled. The mixture was diluted with toluene and isolated toluene layer washed with water. The mixture was filtered after adding 40 mg of the palladium scavenger 3-mercaptopropyl modified silica gel. The solution was then poured into methanol and a yellow polymer isolated. The polymer was redissolved in toluene and then purified using a short column of silica gel. The solution was rewashed with water, reprecipitated in ethanol, and 0.80 g of polymer isolated having an Mn of 32,800 Da. 

C and H NMR spectra of the polymer isolated after irradiation show the formation of essentially pure p-hydroxystyrene polymer but provide no... 

A preferred synthetic procedure to PAEH concerns the formation of the bisphenolate salt followed by the addition of the activated difluoro, dichloro or dinitro monomer. As an example, the heterocyclic bisphenol is stirred in a mixture of toluene and an aprotic polar solvent such as DMAc, NMP or diphenyl sulfone at 135-140 °C for several hours in the presence of 10 mol % excess of powdered anhydrous potassium carbonate (stoichiometric amount of sodium or potassium hydroxide can be used) under a Dean-Stark trap in a nitrogen atmosphere. Water is removed by azeotropic distillation. A stoichiometric quantity of the difluoro monomer is then added to the slightly cooled reaction mixture. The toluene is removed and the reaction is stirred at 155°C in DMAc for one to several hours. Polymer isolation is performed as previously described. This procedure minimizes hydrolysis of the difluoro monomer, gel formation and molecular weight equilibration of the polymer. 

Linkage analysis of the polymer isolated from suspension-cultured, sycamore cells indicated55,65 ratios of 2-linked rhamnosyl to 2,4-linked rhamnosyl to 4-linked galactosyluronic residues of 1 1 4 (see Fig. 1). 

Glusker (37, 38) attempted to prove that these processes are absent by an estimation of active chains by reaction with C14 labelled C02 or H8(T) labelled acetic acid, followed by measurements of the radioactivity of the polymer isolated. Most of the experiments were carried out with fluorenyllithium as initiator in toluene containing 10% diethyl-ether at —60°. At —78° at least 80% of the polymer chains were found to be active at the end of polymerization. The lowest fraction was appreciably less active. Similar results were obtained at —60° although no examination was made of the fractions of lowest molecular weight. Kinetic experiments indicated a first order decay of monomer concentration after an initial rapid consumption of about 3 molecules of monomer per initiator molecule. The mechanism suggested to explain these results involves rapid addition of fluorenyllithium across the vinyl double bond followed by the rapid addition of three monomer units. At this stage it is... 

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